The eye in the sky that changed our view of the universe
Three years ago on Christmas Day, the James Webb Space Telescope (JWST), the largest and most powerful telescope humans have ever launched into space, had its thrilling debut. Since then, the telescope has revolutionised our view of the cosmos beyond measure. Most importantly, it probed the farthest depths to find the very first stars and galaxies formed in the primordial universe, as well as answered many fundamental questions about how the universe has been changing with time since the Big Bang that occurred 13.8 billion years ago.
The list of discoveries by JWST is long. Nevertheless, listed below are some of the groundbreaking discoveries made by the telescope in 2024 that are reshaping our knowledge of cosmology, and allowing us to see with great clarity the dim boundary of the universe.
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The JWST has spotted five galaxies dating to 200 million years after the Big Bang. Located 13.6 billion light-years away, they are likely some of the first to have formed in the ancient universe. These galaxies will challenge existing theories of galaxy formation while offering distinctive assessments of the evolution of gas, stars, and black holes during the early stages of the universe.
Big black holes
Two galaxies and their supermassive central black holes, each weighing nearly 50 million times the mass of the Sun, were caught by JWST in a "merging dance" when the universe was only 740 million years old. Astronomers are trying to figure out what astrophysical processes could explain how these beasts got so big so early.
Sleeping monster of the early universe
A massive black hole in the early universe that appears to be "napping" after stuffing itself with too much food has been discovered by JWST. Analogous to a bear hibernating after feasting on salmon, this "sleeping monster" seems to have overeaten the gas and dust from the collapsed remnants of dead stars and entered a dormant state in its host galaxy. With a mass 400 million times that of our Sun, this giant ranks among the largest ever black holes observed during the cosmic dawn, just 800 million years after the Big Bang. It continues to consume, albeit at an extremely reduced rate—approximately 100 times less than its maximum capacity—rendering it virtually inactive.
From dead galaxies to mysterious red dots
A trio of gigantic "red monster" galaxies in the newly born universe has recently been spotted by JWST. These colossal galaxies, each possessing a mass equivalent to 100 billion times that of the Sun, are over 12.8 billion years old. This means the stars in these galaxies coalesced at an incredibly fast rate—so fast that they are challenging the existing models of how stars and galaxies first formed.
Einstein's "Zig-Zag" phenomenon
It is a rare cosmic event that occurs when light from one object is duplicated six times due to the warping of space-time caused by two massive galaxies. The JWST has confirmed the phenomenon in a distant quasar, a luminous galactic core powered by a supermassive black hole. This discovery could resolve a critical issue in cosmology, namely, the enigma of dark energy, which drives the accelerated expansion of the universe.
Hubble tension is real
An unresolved controversy in cosmology is the so-called "Hubble tension." It is the discrepancy between the value of the Hubble constant, ascertained through the measurement of distances to distant celestial bodies, and the value obtained from the afterglow of the Big Bang. The constant serves as an essential parameter for comprehending the universe's evolution, its age, and its ultimate destiny. Now, JWST has confirmed that the tension is indeed real, rather than a miscalculation or a problem with equipment, furthering the case that something else―not measurement errors―is influencing the rate of expansion.
Serpens Nebula
For the first time, a nebula that astronomers have long hoped to image directly has been captured by JWST. Situated 1,300 light-years from Earth, it is the Serpens Nebula, a young, star-forming region. Its discovery provides information into the basics of how stars are born. Serpens is only about two million years old, which is very young in cosmic terms.
Precise age of our solar system
Over 3,000 new stars are created every second in the visible universe, which is approximately 95 billion light-years in diameter. Astronomers describe the rotating "pancake" of heated gas and dust encircling these stars as the protoplanetary disc, where planets form. Before the James Webb Space Telescope swung into action, little was known about the precise mechanisms that create stars and planetary systems. Today, thanks to JWST, astronomers have some of the most in-depth information on the forces that form protoplanetary discs, providing insights into the possible appearance of our solar system 4.6 billion years ago.
Life beyond Earth
Telltale signs of life―methane and carbon dioxide―have been detected by JWST in the hydrogen-rich atmosphere of an exoplanet dubbed K2-18b, orbiting in the habitable zone of the red dwarf K2-18. With a size roughly 2.6 times the radius of Earth, making it about half the size of Neptune, it is located 124 light-years away from Earth. These initial observations also provided a hint of the presence of a molecule called dimethyl sulphide, which on Earth is only produced by phytoplankton, a flora of freely floating, often minute organisms that live in aquatic environments. Like land vegetation, phytoplankton uses sunlight and carbon dioxide to produce oxygen and carbohydrates. This finding may change how we look for extraterrestrial life and provide a new perspective into the mysterious sub-Neptune class of exoplanets.
So what's next for the James Webb Space Telescope? The cosmos has perpetually captivated humankind with its mysterious allure and the secrets it conceals regarding our beginnings. To date, the telescope has successfully unravelled many secrets by pushing the boundaries of astronomy and cosmology closer to the beginning of time. It has also uncovered many shortcomings of our current models of the universe. While we are refining our models to account for the shortcomings, we are, at the same time, excited about the unknowns that are hiding in the vast expanse of the cosmos. Suffice it to say that JWST will soon expose the unknowns before us.
Dr Quamrul Haider is professor emeritus at Fordham University in New York, US.
Views expressed in this article are the author's own.
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